I played through the entire game, for the PC, on the 'normal' difficulty mode. First off, it gets big points for having the actors from the movies providing the voices for the characters. The animations for which are pretty spot on for how the actors actually... acted.
There are tons of little nods to the original movies and some times the story goes a little too far out of its way to make connections. The vast majority of the plot takes place at locations from the original movies... which sort of robs the story of a little originality of its own... But, hey, this is a game based on two movies and using the locations makes sense. (If the game had been designed to exactly follow the story line of one of the movies, then I'd have nothing to say, and given the quality of the voice acting, the character models, and the set designs... I think they could have pulled that off easily) The additions to the story line seem pretty well thought out, and the level design is pretty awesome.
The levels all incorporate elements which are destructible. Paintings on walls, statues, pillars, cars. A wide variety of things. If you hit them, the game calculates how much property damage you've caused. Fortunately, the city has you covered... so, it doesn't deduct for your pay for completing missions, and you can use your profits to upgrade your equipment. I had NO trouble acquiring enough cash to buy every upgrade, even the ones I didn't want.
The various ghosts you fight are pretty impressive, too. Some of the "boss" fights can be a little annoying (as in tedious, running back and forth down the same few hallways chasing a ghost), and I DID have to consult the internet once to find a solution to a problem in order to progress. In this case, I had eliminated all of the Ghosts TOO FAST, and the game's script couldn't progress as it was supposed to. So, there are some bugs and potential flaws in the level design.
Some minor, nifty, features of note involve the player's PDA. You can "scan" ghosts and it will display a detailed back story on what they are, who they were, and what weaknesses they may have. It's nice for filling in details of the plot of the movies which were never explained. There's also "artifacts" that can be scanned/collected. These also get a back story, and they'll show up around the firehouse between missions. I'm pretty sure the xbox/ps3 version has achievements associated with the ghosts and artifacts, also.
The "weapons" are interesting as well, and while there are only a few available, they're all.. well... awesome, and the 3-4 Ghost Buster's working with you are fairly effective with them most of the time, and when they aren't, they'll at least give you a hint as to which Proton Pack mode is most effective for what you're fighting. The life system is like a simplified version of Left4Dead, you can be incapacitated, but your buddies can help you up... so you're good as long as some one is still standing. This makes the game very forgiving if it takes you a while to master the art of the trap.
I was, however, unable to cross the streams...
I'd give it a 4 out of 5. The only thing which could improve this would be DLC expansions and multiplayer co-op.